Thread: What is the quickest way to increase a .625" diameter hole by .001"

I need to enlarge a small handful of 0.625" diameter plastic/ptfe-lined sleeve bearing ID's by about .0005" or .001" tops. These have been pressed into a mating part already. These bearings are 1/2" long. The part into which they were installed is about half the size of a bread box and expensive.

I am curious what methods people would use in order to do this quickly (not just for my plastic-lined bearing, but even if the material was aluminum or steel). I may order the reamer if necessary. Are honing or lapping reasonable options?

lapping/honing will leave grit in the soft bearing, no not good! reamer +1

This may sound crude and get me kicked out of the Mensa Machinists Club, but a simple flap wheel on a die grinder works wonders for me when I'm trying to meet a target size.

Stuart

any stone or sandpaper or compound will embed into the soft bearing plastic. then the bearing will forever be a lapp on the axle.

A really sharp reamer! but... soft plastic will easily belmouth if you don't have everything in alignment, so hand drill may be out of the question.

an old toolroom method , is to stone the leading edges of a reamer in the flutes to raise a burr sufficient to cut oversize by about 0.0005 to 0.001.but the reamer does need to be sharp in the first place for it to work.

paul

Why not burnish it? Buy an oversized ball bearing or pin and press it through. You can get a range of sizes, and press successive ones through until you hit tolerance. Retaining the sleeve during the press seems like the hardest part.

I would be concerned about a reamer cutting oversized or not round, especially without good alignment.

Leave it out in the sun.

The old trick of a shop made half round reamer can work wonders in plastic, its naturally not grab by and can be honed to the crucial razor sharp edge.

I would take them out and ream or hone the hole they are pressed in to
Small cuts like that in a plastic were never succesfull for me

Peter from Holland

use a 625 reamer that will fit in the bearing without cutting
Start rotation with the spindle then spray brake cleaner into the bore
Its possible the cooling effect will reduce the bearing id, allowing a small cut with the reamer

Just a thought, never did it before

Mike

Buy a .625 Machine Expansion Reamer. There is a tapered set screw in the end you use to either make it cut smaller or larger by turning the screw. Ideally .625 is the largest size you cut with it then you use the set screw to adjust it when it starts to wear out, but you can make them cut a thousandth or two oversize.

I'd swage it.

Originally Posted by Darklabel85

I need to enlarge a small handful of 0.625" diameter plastic/ptfe-lined sleeve bearing ID's by about .0005" or .001" tops. ...

A set of .125" to .625" -.001 and +.001 reamers are very handy for interference or loose fits. Of course a set of exact sizes is obligatory.

Originally Posted by S_W_Bausch

Leave it out in the sun.

Sub it out to the S W Bausch. Sounds like he can get any volume of them done in a day....As long as it's not overcast.

Take a hss .625 reamer and drag a piece of steel along one of the flutes to create a burr in order to make it cut oversize.

Originally Posted by Halcohead

Why not burnish it? Buy an oversized ball bearing or pin and press it through. You can get a range of sizes, and press successive ones through until you hit tolerance. Retaining the sleeve during the press seems like the hardest part.

I would be concerned about a reamer cutting oversized or not round, especially without good alignment.

Originally Posted by Forrest Addy

I'd swage it.

I'm with these guys.

Its teflon, its half a thou, make sure it lands on their loading dock on a day when it is 2 degrees warmer than the day they rejected them, and do nothing.

If its 6 degrees warmer, you are on the hook for making scrap, even though you did nothing.

I wouldn't touch that job with a ten foot pole.

Aluminum or steel, probably just run a reamer through the damn thing. Teflon, I'd laugh, tell them to send me the shafts and I'll make 'em fit. Breathe on it twice and slip 'em in.

If its teflon lined, like a bond lube, just a few tenths or a thou or 2, sand that shit, its tough as nails. Best bet, take a shaft of the same size that needs to fit, drive it in and spin it.
It's fricken plastic, how long do you think its going to maintain size while running? Its not, it will get bigger.

You have 2 choices, this makes you an ass... explain to your customer that they are stupid, and they should just shove the shaft in and spin it.

If you are a true gentleman, you will shove the shaft in, and spin it, and charge them accordingly. This also makes you an ass for charging them for something
they could easily do them damn selves.

Its fricken plastic!!!!!! .0005 thou on teflon, seriously?????? If its just a coating, bust that shit out of there. WOW!!!!?????

I'm not picking on you, I'm picking on your customer. Make some money off of this and let them think you are a genius.

Originally Posted by Darklabel85

I need to enlarge a small handful of 0.625" diameter plastic/ptfe-lined sleeve bearing ID's by about .0005" or .001" tops. These have been pressed into a mating part already. These bearings are 1/2" long. The part into which they were installed is about half the size of a bread box and expensive.

I am curious what methods people would use in order to do this quickly (not just for my plastic-lined bearing, but even if the material was aluminum or steel). I may order the reamer if necessary. Are honing or lapping reasonable options?

Ballising???
ScienceDirect.com - Journal of Materials Processing Technology - A review of ballising: Cold working and its effect on fatigue life
BTW, I know a guy who would send the parts back stating they'd been rectified, (even though they hadn't been!) and await the response!
Cheers
Mike

Unfortunately I didn't have an expansion reamer in 5/8" size, but this is an argument to buy one -- very useful. The customer came by and took the parts despite the tight fit anyways, so its not really a problem anymore.

The first thing that came to mind was the trick mentioned above to kick up a burr on the cutting edges of the reamer such that it cut oversize, but I was hesitant to alter a reamer which I needed for subsequent parts. I'll try getting creative with honing, burnishing, and ballising next time when the part isn't quite so expensive.

BobW, I tried breathing on the parts but it didn't do much.

Thanks for the advice!